Engaging in the middle of a tantrum does two things: it rewards the tantrum by giving it your attention, and it makes it likely that you’ll get caught up, and say or do something that, in the mind of the tantrum-thrower, justifies the tantrum. That’s the fuel the tantrum is looking for–we throw tantrums, hoping people will throw them back.
When you have valuable employees or customers (or kids) who throw tantrums, that might be a sign that there’s something wrong with your systems. The most basic way to decrease tantrums is to find the trigger moments and catch the tantrum before it starts. By creating a way for people to raise their hand, send a note, light a signal flare or otherwise highlight the problem (internal or external) before it leads to a tantrum, you can shortcircuit the meltdown without rewarding it.